Morphology of Flowering Plants, on the exam screen.

Root hairs are fine, thread-like unicellular outgrowths of epidermal cells that develop in the region of maturation (differentiation), where cells have fully elongated and differentiated. Hence option (4) is correct. The root cap, meristematic zone and elongation zone lie nearer the root tip than this region and do not bear root hairs.

Solanaceae flowers are actinomorphic (⊕) and bisexual (⚥) with a gamosepalous calyx K(5), a gamopetalous corolla C(5), five epipetalous stamens A5 (the arc linking corolla to androecium shows stamens attached to the corolla) and a bicarpellary, syncarpous, superior ovary G(2). Only option (2) shows both the fused calyx/corolla and the epipetalous condition, so it is the correct floral formula.

In a racemose inflorescence the main axis keeps growing (unlimited growth) and does not end in a flower; the flowers are borne laterally in acropetal succession, with older flowers at the base and younger ones toward the tip. Termination of the main axis in a flower and limited growth are features of the cymose inflorescence.

Marginal placentation is seen in pea (P-II), axile in lemon/citrus (Q-IV), parietal in mustard (R-I), and basal in marigold (S-III). This yields P-II, Q-IV, R-I, S-III.

Phyllotaxy is the arrangement of LEAVES on the stem or branch, and it comes in three patterns: alternate (as in china rose), opposite (as in Calotropis) and whorled (as in Alstonia). The Greek root phyllon means leaf. The arrangement of flowers on the floral axis is called inflorescence, a separate term. NCERT Class 11, Morphology of Flowering Plants.

The Solanaceae floral formula describes bisexual, actinomorphic flowers with a gamosepalous calyx of five united sepals, a gamopetalous corolla of five petals, and five epipetalous stamens attached to the corolla tube. Statement IV is the odd one out: the ovary in this family is bicarpellary, syncarpous and SUPERIOR, seated above the other floral parts. NCERT Class 11, Morphology of Flowering Plants.

Placentation describes where ovules attach inside the ovary. Marginal placentation has a single ridge along the ventral suture of a monocarpellary ovary, as in pea (P-IV). Axile placentation occurs in multilocular ovaries where the placenta is axial, as in tomato (Q-II). Parietal placentation puts the ovules on the inner ovary wall of a one-chambered ovary, as in Argemone (R-I). Free central placentation has ovules on a central axis with no septa, as in primrose (S-III). NCERT Class 11, Morphology of Flowering Plants.

Roots arising in clusters from the base of the stem replace the short-lived primary root and form a fibrous root system, as in grasses. Chapter: Morphology of Flowering Plants.

Ray florets of Asteraceae are epigynous; the other floral whorls arise above the ovary, so the ovary is inferior. Chapter: Morphology of Flowering Plants.

Plum has a perigynous flower and a half-inferior ovary. Mustard, sunflower and brinjal have superior or inferior ovaries rather than the half-inferior condition asked here. Chapter: Morphology of Flowering Plants.